1. Field of the Invention
The present invention relates to a novel cleaning composition for use in microelectronics manufacturing and a cleaning process and a process for producing a semiconductor device that employ the cleaning composition, and more particularly to a non-corrosive cleaning composition for removing plasma etching residues formed on wafer substrates after plasma etching of metal layers or oxide layers deposited on the substrates and a cleaning process and a process for producing a semiconductor device that employ the cleaning composition.
2. Description of the Related Art
In the manufacture of microcircuits, positive photoresists are used as an intermediate mask for transferring an original mask pattern of a reticule onto wafer substrates by means of a series of photolithography and plasma etching steps. One of the final steps in the microcircuit manufacturing process is the removal of the patterned photoresist films from the substrates. In general, this step is affected by one of two methods. One method involves a wet stripping step in which the photoresist-covered substrate is brought into contact with a photoresist stripper solution that consists primarily of an organic solvent and an amine. However, stripper solutions cannot completely and reliably remove the photoresist films, especially if the photoresist films have been exposed to UV radiation and plasma treatments during fabrication. Some photoresist films become degenerated by such treatments and are more difficult to dissolve in the stripper solution. In addition, the chemicals used in these conventional wet stripping methods are sometimes ineffective for removing inorganic residual materials formed during the plasma etching of metal or oxide layers with halogen-containing gases.
An alternative method of removing a photoresist film involves exposing a photoresist-coated wafer to oxygen-based plasma in order to burn the resist film from the substrate surface in a process known as plasma ashing. Plasma ashing has become more popular in the microcircuit manufacturing process because it is carried out in a vacuum chamber and, hence, is expected to be less susceptible to airborne particulate or metallic contamination.
However, plasma ashing is also not fully effective in removing the plasma etching by-products noted above. Instead, removal of these plasma etching by-products must be accomplished by subsequently exposing the photoresist film to certain cleaning solutions. Several commercial products are now available to clean the plasma etching by-products left by plasma etching followed by plasma ashing. For example, EKC 265, available from EKC Technology, Inc., is a post etching cleaning solution composed of water, alkanolamine, catechol and hydroxylamine. Such a composition is disclosed in U.S. Pat. No. 5,279,771 to Lee. ACT 935, available from Ashland Chemical, is another post etching cleaning solution and is composed of water, alkanolamine and hydroxylamine. Such a composition is disclosed in U.S. Pat. No. 5,419,779 to Ward. ELM C-30, available from Mitsubishi Gas Chemical, is composed of water, N,N-dimethylformamide, a fluorine compound, organic carboxylate, and a sugar alcohol, wherein the sugar alcohol acts as a corrosion inhibitor. Such a composition is disclosed in U.S. Pat. No. 5,630,904 to Aoyama et al.
These commercial products can effectively dissolve plasma etching residues, however, they can also attack the metallic and oxide layers deposited patternwise on the substrate. This is because the pH of EKC 265 and ACT 935 is above 11 and ELM C-30 contains a fluorine compound. The corrosion inhibitors used in these products are not completely effective in stopping corrosion, because metal layers such as copper, aluminum or aluminum alloys (e.g., Al—Cu—Si), and the like are particularly corrosion sensitive. Furthermore, while the addition of a suitable corrosion inhibitor is essential to prevent corrosion of the substrate metal layers, some corrosion inhibitors tend to inhibit the removal of the plasma etching residue and/or form an insoluble film deposited on the metal substrate surface.
Therefore, there remains a need for a new type of cleaning composition for removing plasma etching residues from substrates. Additionally, there remains a need for such a cleaning composition that does not deleteriously affect the substrate. Further, there remains a need for such a cleaning composition that is aqueous-based, non-hazardous and will not harm the environment.
With respect to corrosion of copper, aluminum, an aluminum alloy, etc., Honda et al. have devised a cleaning composition comprising (a) water, (b) a hydroxylammonium compound, (c) a basic compound, and (d) an organic carboxylic acid. This enables corrosion prevention to be achieved while maintaining cleaning properties. This is described in Japanese registered patent No. 3871257.
Furthermore, Honda et al. have constructed corrosion prevention techniques as disclosed in Japanese registered patent Nos. 3513491 and 4147320.
The techniques described in Japanese registered patent Nos. 3871257, 3513491, and 4147320 disclosed by Honda et al. employ a water-based composition, and enable not only metal corrosion to be prevented but also harm to the environment to be avoided.
However, accompanying recent progress in semiconductor substrate production technology, since integrated circuits having various metal layers and insulating film layers (aluminum, aluminum/silicon/copper, titanium, titanium nitride, titanium/tungsten, tungsten, silicon oxide, polysilicon crystal, etc.) are fabricated, the composition of a plasma etching residue is complicated, and there are cases in which its removal cannot be carried out sufficiently. There is therefore a desire for a cleaning composition that removes such residue without causing a problem with metal corrosion.